Checking means for pulse counting circuit



May 20, 1952 A. E. BACHELET CHECKING MEANS FOR PULSE COUNTING CIRCUITS Original Filed Jan. 7, 1950 2 SHEETS-SHEET l INVENTOR By A. E. BACHELET.

A TTORNEV 2,597,42&

May 20, 1952 A. E. BACHELET CHECKING MEANS FOR PULSE COUNTING CIRCUITS Original Filed Jan. 7, 1950 2 SHEETSSI-IEET 2 lNl/ENTOR A. E. BACHELET A T TORNEV Patented May 20, 1952 CHECKING MEANS FOR PULSE COUNTING. CIRCUIT Albert E. Bachelet, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated; New York, N. Y., a corporation of New York Original application January 7, 1950, Serial No. 137,452. Divided and this application March 31, 1951, Serial No. 218,618

8'Claims. (Cl. 177-311) This invention relates generally to signaling systems and more particularly to arrangements insuch systems for detecting and counting signal impulses.

The invention has for its main object to improve gas tube countingchains. In present-day signaling systems, such as may be used with automatic telephone systems, continuous improvement is being sought to increase thespeed of response and the reliability of circuits used'for detecting and counting signals. In the telephone field in particular, continuous energy is expended toward developing circuits which will respond more accurately and more reliably at-a-rapid-rate to signals, such as dial pulses or the like. An exemplary embodiment of the present invention is shown herein as incorporated in an automatic telephone system of the cross-bar type, such as disclosed in Patent 2,585,904 to A. J. Busch of February 19, 1952. A skeletonized disclosure of the Busch system is shown in another copending application of J. W. Dehn, Serial No. 57,398, filed October 29, 1948. The Dehn disclosure shows some details of an originating register circuit of the cross-bar system which circuit is shown herein modified to. embody the present invention.

Thefunction of an originating register, among others, in the cross-bar system disclosed by Busch and Dehn, is to receive,'detect, count, and register dial pulse digits transmitted thereto by a calling subscriber during the initiation by the latter of a request for a connection. It is the improvement of such counting circuits with which the present invention, in one of its forms, finds utility in improving the reliability of response of such originating registers and in simplifying such registers.

Briefly, the present invention contemplates a chain of gas-filled tubes for counting impulses and means for applying all impulses to all tubes at the same time. Circuit means i provided for interconnecting said tubes whereby a first impulse will fire only, the first tube and whereby the firing of any one tube conditions the other tubes such that onlythe next succeeding tube fires on the next pulse. Therefore, the firing of successive tubes in the chain corresponds to a succession of impulsesin a series. Arrangement is made to recycle the chain at the end of a series of impulses such that the chain .will count the next series as before for the first series. A check circuit is provided for detecting the failure of any tube to fire when it is supposed to fire in response to an impulse.

The checking circuit improvement character-- izes the present invention over the prior ;art:and such circuit is shown embodied in a counting circuit disclosed and claimed in application Serial No. 137,452, filed January 7,1950 by A. E. Bachelet and F. K. Low and allowed February 14, 1952, of which this application is a division, which circuit is a variety of the type disclosed and claimed in a copending application of J. W. Dehn, Serial No. 136,008, filed December 30, 1949 and entitled Pulse Counting and Registration System." The checking means comprises a gas tube arrangement, the starter electrode circuit of which is energized by each pulse which is applied to the counting tube chain. A delay means is interposed in the starter electrode circuit of the checking tube such that the impulse is not effective to fire-that tube until after a measurable delay'time. The circuit arrangement is such that if at the duration of this delay time no counting tube has been fired, the checking tube will fire to indicate trouble. If, however, a counting tube has fired, the checking tube will be prevented from firing.

The main object of the present invention is the provision of the above outlined checking circuit means for a gas tube counting chain. Other features, particularly pointed out in appended claims, will be apparent from the subsequent detailed exemplary embodiment of the invention, the drawings of the disclosure being described generally a follows:

Figs. 1 and 2 combined show parts of a crossbar originating register embodying the present invention;

Fig. 1 shows the pulse detecting and counting circuit embodying the invention; and,

Fig. 2 shows circuit means for registering the digits counted.

GENERAL DESCRIPTION The present invention is herein disclosed as embodied in an automatic telephone system such as is disclosed in the Busch Patent 2,585,904. Busch discloses in detail a cross-bar system wherein originating register circuits are used for transmitting dial tone to calling subscribers, counting'pulses of called digits, registering the called digits, and seizing an idle marker circuit for the purpose of having such a marker complete the desired connection. Since the presentinvention relates particularly to pulse counting-and registering circuits only certain portions of an originating register circuit have been disclosed and described herein.

Another copending application of J. W. Dehn, Serial No. 57,398, filed October 29, 1948, discloses a skeletonized arrangement of the Busch disclosure including an originating register circuit in some detail. The Dehn and Busch disclosures may be referred to for details omitted from the present description as unnecessary for a complete understanding of the present invention.

The register relay arrangement shown in Fig. 2 is a variety of relay circuit arrangements disclosed and claimed in an application of F. K. Low, Serial No. 137,323, filed January 7, 1950, and entitled Pulse Counting and Registration Circuit.

As may be obtained from the Busch or Dehn disclosure, the general sequence of events during the originating of a call by a subscriber is as follows:

(1) The calling subscriber lifts his receiver thereby seizing an idle marker circuit and automatically informing the seized marker that a dial tone connection is desired;

(2) The seized marker tests for and seizes an idle originating register circuit;

(3) The marker interconnects the calling line with the seized originating register circuit over the cross-bar switch train and then the marker releases;

(4) The originating register transmits dial tone to the calling subscriber;

(5) The calling subscriber dials the digits of the called number or other desired destination;

(6) The originating register receives, follows, and counts the pulses of each digit and registers such digit;

(7) When sufficient digits have been registered therein the originating register seizes an idle marker circuit and transfers thereto, among other items of information pertaining to the call, the digits so registered; and,

(8) The marker, when it has received all of the information from the originating register, releases the originating register, completes the call, and then releases itself.

Since the present invention is embodied only in circuits of an originating register, in so far as the present disclosure is concerned, the subsequent description will not cover items 1, 7, and 8 above. 'Such matters are fully dealt with by Busch and Dehn and are not necessary to the present description.

DETAILED DESCRIPTION Seizure of originating register When the marker seizes an idle originating register circuit such as is disclosed partly in Figs. 1 and 2, the off-normal relay On(I) thereof is operated by the marker.

Relay ON(I). upon operating, partly prepares the originating register circuit for operation as follows:

(1) Ground is applied over contact 6 of relay ON( I), contact 5 of relay P2( I) when relay P2(I) is operated, to the armatures of relay RAII) associated with contacts 9 and I of that relay and, when relay RA(I) 'isoperated. extending over conductors I00 and IOI to Fig. 2 for purposes to be described hereinafter;

(2) Ground is applied over contact of relay ON(I), contact 2 of relay A5( I), to negative battery through the winding of relay B5(I whereupon relay B5(I) operates;

(3) Ground is applied over contact 5 of relay ON(I) to the lower winding of relay P2(I) for the purposes of locking relay P2( I) operated, as will be described hereinafter;

(4) Ground is applied over contact 3 of relay ON(I), conductor I02, contact 1 of relay HS(2), contact 1 of relay BS(2), to negative battery through the winding of relay AS(2), whereupon relay AS(2) operates:

(5) Ground is applied over contact 2 of relay ON(I), through resistance I03, to condenser I04 of the pulse forming network I23, comprising windings I05 and I06 and an asymmetrical resistance, such as dry rectifier I08, connected between negative battery and the upper armature of relay SR.(I)

(6) Positive battery is connected over contact I of relay ON(I) to the off-normal battery conductor I09; and,

(7) Ground is connected over contact 4 of relay ON(I) to conductor H0 and thence in parallel through resistances 200, 20I, 202, 204, and 201 for the A digit register relays A0(2), AI (2), A2(2), A4(2), and A'I(2), and through resistances 2I0 through 2H for the B digit relays B0(2) to BI(2), and likewise through resistances 210 to 211 for the H register relays H0(2) to HI(2) and through the winding of each such relay to negative battery.

In regard to item (7) above, each of the register relays of Fig. 2, such as relay A0(2), will conduct a current limited by the resistance in series therewith, such as resistance 200. This amount of current will be referred to hereinafter as the holding current, which is insufllcient to operate a relay but is sufficient to hold a relay operated once it has been operated by an additional amount of current. Since these register relays of Fig. 2 utilize only front or make contacts a preferred embodiment thereof may be the magnetic reed type of relay such as is disclosed in the Patent 2,289,830 to W. B. Ellwood of July 14, 1942,

In regard to item (5) above, when ground is applied over contact 2 of relay ON(I) and through resistance I03 to the right-hand side of condenser I04, the left-hand side of condenser I04 is driven temporarily to substantially ground potential. At this instant the dry rectifier I08 represents a high impedance to this pulse. These rectifiers, such as rectifier I08, are arranged such that when the arrow side thereof is positivev with respect to the other side of the rectifier, said rectifier will represent a low impedance, and when the reverse polarity situation occurs, said rectifier will represent a high impedance. Under the assumed condition, at which time ground appears on the left-hand side of condenser I04, rectifier I08 represents a high impedance for this pulse. Condenser I04 will charge very quickly in a circuit including negative battery, through the winding I08, through condenser I04 and resistance I03, to ground over contact 2 of relay ON(I). The fairly large charging current for condenser I04 passing through the coil I06 induces into the other coil I05 a total voltage with reference to negative battery of approximately volts positive, which appears on the upper armature of relay SR(I). Since relay SR(I) is not operated at this time 100-volt positive pulse is ineffective. The lefthand side of condenser I04 returns to substantially negative battery potential as soon as condenser I04 becomse fully charged. Therefore, on the upper armature of relay SR(I) there will appear a short pulse of approximately 100-volt amplitude-in a positive direction with respect to negative battery.

In regard to item (6) above, positive'battery isappli'ed over'contact I of relayON(I) --to the ofi-normal battery conductor I09, through condenser I01, to the starter electrode of tube ST( I). Since the cathode of tube ST(I) is at negative battery potential through resistance I90, tube ST(I) will fire and the discharge will transfer to -a circuit extending from negative battery, through resistance I90, to the cathode of tube ST(I), across the main gap discharge path-of tube-ST(I), through resistance land through impedances H2 and H3, to positive-battery on conductor I09. The presence of condenser II I connected to the cathode of tube ST(I) will effectively'hold the cathode of tube ST(I) at meative-battery-potential during'the initial transient-period. Eventually, condenser Ill willbecome charged to a potential onthe cathode of tube ST(I) which is approximately 100 volts positive with respect to negative battery.

Interconnection between calling subscriber and originating register bar switch train between the seized register and the calling line, thereby closing the ring and tip conductors H 9 and I of the register over the calling li-ne loop. Relay L(I) is operated in a circuit extending from ground through the upper left'secondary winding of the dial tone transformer I2I, conductor I20, over the switch train and the line loop, back over conductor II9, through the lower left secondary winding of the dial tone transformer I2 I, and through the winding of relay L(I) to negative battery. Relay L(I), upon operating, operates relay SR(I) in an obvious circuit over contact I of relay L(I). Relay SR(I), upon operating, closes at its contact I a circuit from the pulse network or pulse transformer I23-to the pulsing conductor I22 for a purpose to be described hereinafter.

' The structure of the relay L(I) is preferably,

but not'necessarily, of the mercury contact type similar to the structure of the mercury contact relay disclosed in Patent 2,577,602 of December r 4,'1951'to E. T. Burton. The armatures, or armature, of relay L(I) are biased towards the contacts 2 and 4. This bias, as in the type of relay disclosed by Burton, may be both partly mechanical due to the usual spring and partly magnetic due to the presence of a permanent magnet, if desired, influencing contacts 2 and 4. When relay L(I) is operated, under closed loop conditions, the current fiow through the right winding is arranged to counteract partly the effect of the current flowing through the left winding. This, in effect, increases the total bias tending to release the armatures when relay L(I) is operated. This is to improve the releasing response of relay L( I thereby aiding its performance under line conditions which tend to retard the release of relay L(I). The purpose of the middle winding in series with condenser C(I), is well known to provide a measure of pulse correction action, as described forinstance in Patent'2,029,723 to L. H. Johnson and F. K. Low of February 4, 1936.

Itwill be observed that prior to the operation of relay L(I), negative battery was applied over contact I-of relay L(i), throughresistanceHS,

andthrough condenser II6 to ground, whereby condenser II6 was charged at its upper plate to a potential of negative battery. Upon the operation of relay L(I), condenser II 6 will-begin to acquire a charge positive with respect to negative battery in a circuit extending from posi tive battery over contact I of relay ON(I) through resistance I24,'through the winding of relay RA( I) through resistance I26, and through condenser II6 to ground. Condenser II 6 will thereupon begin to acquire a positive charge with reference to the negative charge that it previously had acquired. If relay L( I remains operated for a-suflicient length of time, condenser II6 will, during that-time, acquire a sufiicient charge of positive potential with respect to negative battery on the cathode of tube- RAH) tov cause an ionization across the starter-electrode gap from cathode of tube RAM) to the-starter electrode II I of tube RAH).

Assuming for the present that the calling subscriber delays-before dialing the additional digit for a suilicient time to permit condenser II6 to acquire such a charge, tube RA(I) will fire, thereby causing a discharge across the main gap in a circuit extending from negative battery to the cathode of tube RA(I across the main discharge path of tube RA(I) to the main anode II8, through the winding of relay RAH), through condenser I25 (which, underthe transient condition, represents substantially a short circuit across resistance I24) to off-normal positive battery on conductor I09. Relay RA( I) will operate in this circuit, locking over its contact 6 to negative battery over contact 3 of relay L( I This negative locking battery for relay R.A( I) extendsback to the main anode of tube RA(I)' thereby extinguishing tube RA(I). Relay (RAG), upon operating, accomplishes no useful function at this time. The operationof relay RAH), as with the discharge through tube RA(I), is for the purpose'of timingthe interdigital pause for-extending the pulsecount to the registers of Fig. 2, as will be explained hereinafter.

Upon the first release of relay L( I) responsive to the first open line period of the-first pulse, relay RAH) will be released and condenser IIB will be fully discharged over contact 4 of relay L( Dial tone is transmitted from the source I 21 thereof, through transformer I2I, to the calling subscriber who may then begin to dial the called number. It will be assumed that the calling subscriber begins to dial the initial digit before condenser II6 can acquire sufficient charge to fire tube RA( I as above described.

Counting initial digit of one An initial digit of one pulse, unless followed directly by a second digit of one pulse as will be explained, is assumed not to be a legitimate signal, because of the frequency with which such erroneous indication may be eifected by accidental manipulation of the subscribers dial, by spurious electrical impulses, etc. Such an initial digit is absorbed on the basis of the above assumption; but, as will beexplained, it is not discarded in view of the fact that a seconddigit of one pulse is presumed to indicate a legitimate 11 prefix for a toll directing code or special service code of 11X, where X may be any digit from 2 to 9.

Whenrelay L(I) releases, in response to the first-open loop period of the first pulse of the first digit, condenser H6 in the starter electrode circuit of tube RAH) will be discharged as previously described over contact 4 of relay L(I), and relay RAH) will be released if it had previously been operated. Relay SR(I), due to its slow-releasing characteristic, will remain operated during the release periods of relay L( I) representing pulses of digits.

Upon the first release of relay L(I), negative battery is applied over contact 2 of relay L(I), contact 2 of relay SR( I) to condenser I04. Since at this time the left-hand side of condenser I04 is held substantially at negative battery, the application to the right-hand side of condenser I04 of negative battery will drive the left-hand side of condenser I04 to a potential which will be approximately negative battery plus negative battery; that is, assuming that negative battery is 48 volts, if -48 volts is applied to the righthand side of condenser I04, the left-hand side thereof will be driven temporarily to approximate 96 volts. It will be observed that under these conditions the upper or arrow side of rectifier I08 will be substantially 48 volts more positive than the lower plate of rectifier I08. Under these conditions rectifier I08 represents a very low impedance shunt across the winding I06 of transformer I23 thereby precluding any substantial negative pulse over contact I of relay SR(I). Therefore, release of relay L(I) will not substantially affect the pulsing conductor I22 which is in circuit with the starter electrodes of the counting tubes PI (I) through P5(I).

At this time it will be observed that contact I of relay SR(I) is substantially at negative battery potential and consequently condenser I26, in the starter electrode circuit of tube CK( I will have acquired a charge of substantially negative battery in the circuit including resistor I29, contact I of relay SR(I) to negative battery through the windings of transformer I23.

Upon the reoperation of relay L( I at the end of the first pulse of the first digit, condenser H6 in the starter electrode circuit of tube RA(I) is permitted to begin to acquire a charge, as above described, for measuring the interdigital pause. Relay L(I), upon reoperating, reenergizes relay SR(I) and removes at contact 2 of relay L(I) negative battery from the right side of condenser I04. Ground will again be applied over contact 2 of relay ON(I) to the right-hand side of condenser I04 thereby, during the transient period, driving the left-hand side of condenser I04 to substantially ground potential. Under these cir cumstances it will be appreciated that varistor or dry rectifier I08 will have a voltage condition thereon whereby the upper or arrow side of the rectifier will be some 48 volts negative with respect to the lower plate thereof. Under these circumstances rectifier I will represent a high impedance and charging current for condenser I04 will be permitted to fiow through the winding I06 of transformer I23. As a result of the fiow of this current through winding I06, approximately a 100-volt pulse is produced at contact I o f relay SR(I) by autotransformer action through the coil I of transformer I23. This positive pulse of approximately 100 volts with respect to negative battery appears on the pulsing conductor I 22.

It will be observed that the pulsing conductor I22 is connected in parallel to the starter electrode circuits of all of the tubes PI(I), P2(I), P3(I), P4(I), P5(I.) and A5(I) through respec tive resistances I3I, I32, I33, I34, I35 and I36 8. and through respective condensers I6I, I62, I63, I64, I65 and I66. It will also be observed that the cathodes of tubes PI(I), P3(I), P4(I) and P5( I) are connected to negative battery through 5 respective resistances I5I, I53, I54 and I55 and that the cathode of tube P2(I) is connected to negative battery through the upper winding of relay P2(I) and over contact 3 of relay P2(I) Each of the tubes P2(I), P3(I), P4(I), P5(I) and A5(I) has associated therewith a rectifier I42, I43, I44, I45 and I46 connected between the starter electrode circuit of the associated tube and the cathode of the previous tube, such as rectifier I46 for tube A5(I) connected between the junction of resistance I36 and condenser I66 to the cathode of tube P5(I) Rectifier I, associated with tube PI(I), is connected to the cathode of tube ST( I) through an additional rectifier I30 having in parallel therewith a condenser I50 for a purpose to be described hereinafter. Rectifier I4I associated with tube PI(I) is also connected to negative battery through an additional rectifier I40 and resistance I55 in the cathode circuit of tube P5(I).

The above-described rectifier circuit arrangements, associated with the various tubes of the counting chain, are arranged such that at this time tube PI(I) is the only tube which can fire in response to the first positive pulse on pulsing conductor I22. Since tube ST(I) is the only tube which is conducting at this moment the cathodes of tubes PI(I), P2(I), P3(I), P4(I) and P5( I) will all be held at substantially negative battery potential. Since the positive pulse on conductor I22 is approximately 100 volts positive with respect to negative battery, it is obvious that for all parts of this positive pulse the rectifiers connected to the cathodes of tubes PI (I) through P5( I) represent substantially a low impedance shunt to said pulses. Therefore, none of the tubes P2(I) through A5(I) can fire in response to the first positive pulse on conductor I22.

Since tube ST(I) is conducting, its cathode, due to the voltage drop across resistance I90, will be maintained at approximately 100 volts positive with respect to negative battery. Therefore, rectifier I30 will represent a low impedance to the positive pulse on conductor I22. At the same time, the right-hand or arrow side of rectifier I40 is held substantially at negative battery potential on the cathode of tube P5(I), thereby making rectifier I40 a high impedance with respect to the positive pulse on conductor I 22. Under these circumstances the rectifier I4I connected to the. starter electrode circuit of tube PI(I) will represent a high impedance to the positive pulse on conductor I22 thereby ionizing the starter gap;

of tube PI (I) and permitting a discharge there- 00 through in a circuit extending from negative battery through resistance I 5I, cathode of tube PI (I) tothe main anode of tube PI(I), through the common anode load for all the pulse tubes consisting of resistance II I and impedances H2 5 and II 3 to positive ofi-normal battery on conductor I09.

When tube PI(I) fires, as above described in.

response to the first positive pulse on the pulsing conductor I22, it causes an additional voltage drop in the common anode load including re. sistance II I for all of the pulse counting tubes thereby reducing the main anode voltage on tube ST(I) to such a value that tube ST(I) extinguishes. When tube ST(I) extinguishes it cannot refire due to the following two considerations:

(1) The cathode of tube ST(I) is held temporarily at substantially 100-volt positive potential with respect to negative battery by reason of the presence of condenser H4; and,

(2) Condenser I01 in the starter electrode circult of tube STU) has on the right side thereof a charge of substantially negative battery potential.

Eventually the positive charge on condenser II4 will be discharged through resistance I90 thereby raising the cathode of tube ST( I) to substantially negative battery potential to, in efiect, make rectifier I30 appear as a high impedance to positive pulses on conductor I22. When tube PI(I) fired, as above described thereby reducing the available main anode voltage for tube ST(I) to extinguish the latter, the condenser I52 connected to the cathode of tube PI(I) maintains substantially negative battery potential temporarily on the cathode of tube PI (I) such that the drop in the main anode voltage will not be suificient to prevent tube PI(I) from firing. Eventually, condenser I52 charges up to substantially 100 volts positive with respect to negative battery due to the discharge current flowing through resistance II in the cathode circuit of tube PI (I). The approximately 100-volt rise in the positive direction of the potential of the cathode of tube PI I) will be recognized, in view of previous discussion, as reversing the polarity of voltage across rectifier I42 thereby, in effect, causing rectifier I42 to appear as a high impedance to any subsequent positive pulse on conductor I22. This, in efiect, conditions tube P2( I) to fire on the next pulse.

Under the conditions when tubes ST(I) and P5(I) are both not conducting, as is the condition for the next pulses on conductor I22, it will be appreciated that rectifiers I40 and I30 both represent a high impedance to a positive pulse which may occur on the pulsing conductor I22. For the cases where it is desired that the next pulse on conductor I22 will fire tube P3(I), or P4(I), or P5(I), it is not desired that this pulse also be effective to fire tube PI(I). For those cases condenser I50, which is in shunt of rectifier I 30, is effective under the transient conditions concurrent with the sharp positive pulse on the pulsing conductor I22, to represent substantially a short circuit around the rectifier I30 thereby in effect placing the bottom side of rectifier I4I at substantially negative battery potential from the cathode of tube STU) making rectifier I iI substantially a low impedance shunt for these pulses'on conductor I 22. V As has been mentioned previously, upon the reoperation of relay L( atthe end of the first pulse, condenser I56 was permitted to begin acquiring a positive charge in a previously described circuit extending from ground through condenser I I6, through resistance I 26, through the Winding of relay RAH), through resistance I24 to positive off-normal battery on conductor I09. The time constant of this charging circuit is such that if the reoperation of relay L( I) lasts for a short interval of time representing merely a pause between pulses of a digit, then condenser IIfi will not acquire suffieient charge by the time relay L(I) again releases to discharge condenser H6 to fire tube RAH); but, if the recperation of relay L(I) lasts for a relatively long interval of time representing an interdigital pause, then condenser II5 will acquire suiiicient charge, before relay L( I) again releases, to fire tube RA(I).

. As hasbeen assumed, the first pulse is considered to represent acne-pulse dig-it. Relay L(I) will remain operated'long enough to permit the condenser I IE to acquire a charge sufficient to fire tube RA( I When tube RA( I) fires, as has been previously described, the main discharge occurs in a circuit extending from negative battery across the main discharge gap of tube'RA(I), through the winding of relay RA( I through condenser I25 to positive battery on conductor I09. Relay RA( I) operates in this discharge path and locks over its contact 6 to negative battery over contact 3 of relay L(I). This negative locking battery is extended back to themain anode II 8 of tube RA( I), thereby extinguishing tube RA( I) and discharging condenser I I6.

. Relay RA( I upon operating, extends a circuit fromv the cathode of each of the tubes P5(I), P4(I), P3(I) and P2(I) over respective contacts I, 2, 3 and 4 of relay RA(I), to respective pairs of rectifiers I3'I-|38, I39-I4'I, I48-I49- and 156-451. Likewise the cathode of tube PI(I) is extended overcontact 5 of relay RA(I), contact I of relay P2( I to condenser I60 associated with tubes IIA(I) and IIIB(I). If relay P2(I) were operated, under conditions to be described hereinafter, theconnection from the cathode of tube PI (I) would be extended over contact 2 of relay P2( I) to the pair of rectifiers I58--I 59.

Conductors I70, "I, I72, I14 and I1! exten over respective contacts 5, 4,.3, 2 and I of relay AS(2) to the left-hand sides ofthe windings of respective A- digit register relays A0(2), AI(-2),, A2(2-), A4(2) and A'I(2).. Two out of these five conductors are to be energized by positive battery thereon, on a two-out-of-five code basis, for operating two of the five A digit register relays of Fig. 2 in accordance with the following code:

' Conductors Conductors Dig; Energized Dlglt Energized The cathode circuits of all tubes, which are extended by the operation of relay RA( I) to the pairs of rectifiers above described, are all at substantially negative battery potential, thereby in efiect making the top four pairs of rectifiers high impedances. The bottom two rectifiers I58I59 have no potential on their arrow sides due to the fact that relay P2(I) is not operated at this time. Thus, none of the A digit register relays of Fig. 2 will be operated in response to the counting of the initial one-pulse digit, and such initial one-pulse digit is absorbed in a manner to be described shortly.

Due to the fact that relay P2(I) is not operated; thepositive voltage of substantially 100-volt value with respect to negative battery on the cathode of tube PI (I) is extended over contact 5 of relay RAH), contact I of P2(I), to the condenser I60 as previously described- Before relay RA(I) operated, condenser I60 was charged to negative battery potential on its right side in a circuit extending from ground through resistance I16, through condenser I60, and through resistance I to negative battery. When the positive voltage of approximately volts positive with respect to negative battery is extended from the cathode oftube PI (I) to the right side of'condenser I60, this positive voltage drives the left-handside'of condenser. I60temporarily to a voltage of approximately 100 volts positive with respect to negative battery. At this point the polarity of rectifier I61 is such as to represent a high impedance to this pulse. This positive voltage will-quickly charge condenser I80 to the positive voltage value whereupon the left-hand side of condenser I60 will rapidly rise to about 100 volts and then return again to substantially ground potential. This positive pulse on the lefthand side of condenser I60 is applied through resistance I69 and condenser I18 to the starter electrode of tube I IA( I whereupon tube I IA(I) fires and a discharge occurs from ground through condenser I8I, cathode of tube IIA(I), across the main anode discharge path of tube IIA(I), through the anode load resistance I85 to positive battery on the oil-normal conductor I08. Since the cathode of tube IIA(I) is held temporarily at substantially negative battery potential by the presence of condenser I8I, the rectifier I19 connected to the cathode of tube IIA(I) will represent a low impedance shunt to the positive pulse as far as the starter electrode circuit of tube IIB( I) is concerned. Tube I IB( I) therefore will not fire on this first positive impulse.

Relay RAH) upon operating extends, over its contact 8, positive battery on conductor I09 to the. junction between resistances I86 and I81 associated. with the starter electrode circuit of tube ST(I). This positive voltage discharges condenser I01, driving the starter electrode of tube ST(I) sufliciently in the positive direction to ionize tube ST(I); whereupon tube ST(I) discharges in a circuit including ground through condenserI I4 cathode of tube ST( I across the main anode discharge path of tube ST( I to the main anode of tube ST(I), through the anode load III common to all counting tubes, to positive battery on conductor I09. Since the main anode of tube PI (I) is supplied by positive battery through the same common anode resistor I II, as was the main anode of tube-ST(I), the reduction of main anode voltage due to the additional discharge through tube ST( I) will reduce the main anode voltage of tube PHI) to such a value as will cause the extinguishing of tube PHI), as has been previously explained. This reverts the starting chain to its initial condition preparatory to receiving, detecting, and counting the number of pulses in the second digit.

A second digit of one pulse If a second digit of one pulse is receivedand counted by the originating register circuit, it is assumed that this is alegitimate indication of a 11 prefix to a toll directing code or to' a special 11X code of a service nature.

When relay L(I) releases in response to the first open line loop 'period pulse of the second 'digit, condenser H6 is discharged over contact 4 of relay L(I) and negative battery is applied over contact 2 of relay L(I), contact 2 of relay SRO), to the pulse transformer I23 which, as

, has been previously explained due to the presence of the rectifier I08, shunts or short-circuits this negative pulse such that it is not efiective on thepulsing conductor I22.

' When relay L(I) reoperates at the end of the first pulse of the second digit, condenser I I6 is permitted to begin to acquire a charge to measure the interdigital timing, as has been previously explained, and the removal of negative battery from contactv 2 of relay L(I) causes the pulse transformer I 2 3 to produce a positive pulse on the pulsing conductor I22 as has been explained 12 above. (Relay RA(I) was released when relay L( I) released during the first pulse of the second digit.) The first pulse on pulsing conductor I22 fires tube PI(I) and the firing of tube PI(I) extinguishes tube ST(I).

Under the assumption that this second digit is also a one-pulse digit, condenser II6 will acquire sufficient charge to fire tube RA( I thereby operating relay RA(I), which relay locks under the control of the operated relay L(I), as previously explained. extinguishing tube R-A(I) and discharging condenser I I6. Upon the operation of relay RA(I) as above, the positive voltage on the cathode of tube PI (I) is extended over contact 5 of relay RA(I), contact I of relay P2(I) to the right-hand side of condenser I60 thereby producing on the left-hand side of condenser I60 the above-mentioned short positive pulse. By this time the condenser I8I in the cathode circuit of tube IIA(I) has acquired a charge of substantially volts positive with respect to negative battery at the cathode of tube I IA( I thereby reversing the polarity across the rectifier I19 and making it appear as a high impedance to the next positive pulse from condenser I60. This second positive pulse through condenser I60 therefore will be transmitted through resistance I68 to the starter electrode of tube IIB(I) firing tube I I B( I) in a discharge circuit extending from negative battery through the winding of relay IIX(I), resistance I83, across the cathode-main anode discharge circuit of tube II B(I), through the anode load I85, common to tubes IIA( I) and IIB(I), to positive battery on conductor I09.

' The additional drop in voltage through the resistance I85, due to the additional firng of tube IIB(I), reduces the main anode voltage of tube IIA(I) to such an extent that tube IIA(I) extinguishes. Relay IIX(I) operates in the discharge circuit of tube IIB(I) and locks over its contact, through resistance I84, to off-normal positive battery on conductor I09. This positive locking battery, when extended to the cathode circuit of tube IIB(I) over the contact of relay IIX(I), raises the cathode potential of tube IIB(I) to such an extent as to extinguish tube IIB(I) by effectively short-circuiting the main anode gap of tube I IB( I It will be appreciated that any additional onepulse digits which may come along later will be absorbed in the I IA(I) and IIB(I) tube circuits. It will be apparent, as has been previously explained, that no digit of the value of one pulse can be transmitted to the registers of Fig. 2 until relay P2(I) operates, as will be explained later. It will also be appreciated that the operation of the relay IIX(I) may be used for transmitting additional information relating to the receipt and counting of a 11X prefix code to a subsequently seized marker.

Receipt of a digit of value of at least two pulses Let it be assumed that the next digit is of two or more pulses, say four.

When relay L( I) releases during the first pulse of the digit, condenser H6 is discharged and negative battery is applied over contact 2 of relay L(I), contact 2 of relay SR(I), through condenser I04, to the pulsing transformer I 23. When relay L( I) reoperates the end of the first pulse, condenser III; is permitted to start charging to measure the interdigital pause, and condenser I04 is again charged to create a positive pulse on the pulsing conductor I22. Since tube ST(I) is conducting at this time, the varistor I4I will 13 efiectively represent a high impedance to the positive pulse on conductor I22 thereby causing tube PHI) to fire. Tube PI(I) in conducting extinguishes tube ST( I) When relay L(I) releases during the second pulse, condenser H6 is discharged and condenser I04 is discharged.v When relay L(I) reoperates at the end of the second pulse, condenser II6 begins to time the interdigital pause and condenser I4 is again charged to create a positive pulse on conductor I22. The positive pulse on conductor I22 fires tube P2(I) because the rectifier I42 in the starter electrode circuit of tube P2(I) is effectively a high impedance because of the high positive voltage on the cathode of the conducting tube PI (I). Tube P2( I) conducts in a circuit extending from negative battery, contact 3 of relay P2(I), upper winding of relay P2(I), cathode of tube P2(I), main anode discharge path of tube P2(I), to positive voltage on conductor I09 through the common anode load resistance III and impedances H2 and H3. Tube P2(I) in conducting extinguishes tube PI(I) by reducing the voltage at the main anode of tube PI(I) to such an extent as to extinguish tube PI (I). Tube P2(I), in conducting in the abovetraced circuit, operates relay P2 I Relay P2( I) locks in a circuit from negative battery over contact I of relay P2( I) through the lower winding of relay P2(I) to oiT-normal ground over contact 5 of relay ON( I).

In a similar manner, the third pulse fires tube PM I) and extinguishes tube P2( I) and the fourth pulse fires tube P4( I) thereby extinguishing tube P3(I). of the fourth pulse, condenser IIB will begin to acquire a charge to thereby measure the interdigital timing period. As has been assumed, this particular digit contains four pulses, therefore relay L(I) 'will remain operated at the end of the fourth pulse for a length of time sufiicient for condenser H6 to acquire suflicient positive charge to fire the tube R-A( I) When tube RA(I) fires, relay RAH) operates and. looks as prevously described, thereby extinguishing tube RA(I) and discharging condenser II6. Upon the operation of relay RA(I), the high positive voltage existing at the cathode of tube P4(I), due to the fact that the latter tube is conducting, is extended over contact 2 of relay RA(I) to the left-hand or arrow sides of rectifiers I39 and I41. The right-hand sides of rectifiers I39 and I0! extend over respective contacts 2 and 3 of relay B5 I) to respective conductors I10 and I14, over respective contacts 5 and, 2 of, the A digit steering relay AS'(2), to the left-hand sides of the windings of respective relays A0(2) and A4(2). Since the conduction of tube P4(I) makes the left or arrow side of rectifiers I39 and I41 of positive potential with respect to negative battery, these rectifiers will represent low impedance in the above-traced circuits, whereupon relays A0(2) and A4(2) will efiectively have placed on the left-hand sides of their respective windings positive battery. The:

resulting increase of current through relays A0 (2) and A4(2) will produce a value of current suflicient to operate these two relays, whereupon relays A0(2) and AME) operate to register on a two-=out-of-five basis the first orA digit of the value of four pulses.

After the registration in the register relays A0 (2). and'A4(2) of the A digit of four pulses,

tubeH-(I will beextinguished and relay RAM) will subsequently release upon; the releasenf relay When relay L(I) reoperates at the end L(I) during the first pulse of the next succeeding digit. When tube P4(I) is extinguished or when relay RA(I) releases under these conditions, positive battery is removed from the left side of respective-windings of relays A0(2) and A4(2) thereby decreasing the current flowing through thes relays to the original holding value. This value of current, as has been previously explained, however, is sufficient to hold operated any relays of the digit register group which have been operated. Consequently, relays A0(2) and A4(2) will remain operated under the control of ofi-normal ground on conductor I I0. This arrangement of register relays wherein no back or break contacts are necessary for holding circuits may be of the type disclosed in Patent 2,289,830 to W. B. Ellwood of July 14, 1942.

Relay RA(I) upon operating extends positive potential on conductor I09, over contact 8 of relay RAG) to resistance I81 to dischargecondenser I01 and fire tube STU), thereby extinguishing tube P40) and reverting .the pulse counting chain to its normal counting condition.

Furthermore, upon the operation of relay RA( I), ground is extended over contact 6 of relay ON(I) contact 5 of relay P2(I), over'contacts 9 and I0 of relay RA(I), conductors I00 and I01 to the steering relay circuit of Fig. 2. Ground on conductor I00 extends over contact 8 of relay AS-(Z) to hold relay AS(2) operated when the. holding circuit therefor is broken upon the operation of relay BS(2). Ground on conductor I01 is extended over contact. I0 of relay AS(2), to. negative batterythrough the winding. of the B digit steering relay 38(2). Steering relay BS(2) operates in this circuit after the extinguishing of tube PMI). Relay BS(2) looks. over its contact 6 and over contact 1 of relay HS(2) to ofi-normal ground on conductor I02. Theoperation of the B digit steering relay BS( 2) closes the five conductors I10, I1I, I12, I14 and I11 over its respective contacts 5, 4, 3, 2 and I to the B digit register relays B0(2) to 131(2) preparatory to registering the second or B digits transmitted by the calling subscriber.

g It will be observed that the ground circuits on conductors I00 and IOI leading to Fig.2 are not effective until after relay P2(I) operates. This insures that no advance of the steering relays of Fig. 2 is permitted until atleast one digit has been detected and counted which comprises two or more pulses.

It is also to be observed that up to this point relay B5(I) has been operated and relay A5(I has been released. As will be appreciatedfrom subsequent description, relay B5 (I) operates to extend to the register relays of Fig. 2 any digit which has been counted and having five or less pulses in the digit; and, relay A5(I will be 0perated with relay B5( I) released whenever a digit is counted by the circuit of Fig. 1 as containing six or more pulses. The operation of one or the other of relays B5( I) or A5 (I) selectively extends the two-out-of-five conductors from each of the five pairs of rectifiers to various of thefi've conductors leading to the registers of Fig. 2, such that under one condition the conduction to any one of the. tubes. PI (I) through P5(I) may represent either of two different digits depending upon whether the pulse count of a particular digit is below or above 5. For instance, with relay B5( I operated, as in the above example, the conduction of tube PM 1) indicates a pulse count of 4.. However, ifrelay A5(I) wereo-peratedinstead =of.relay; 35H), thenlthe. conduction otfalv tube such as P4(I) would extend positive battery over contact 2 of relay RA(I) through rectifiers I39 and I41, over contacts and 6 of relay A5(I), to conductors I12 and I11, thereby indicating, on a two-out-oi-five basis, the digit 9. Therefore, in one case, tube P4( I) upon conducting indicates the digit 4 (below 5) and, in the other case, conduction of the tube P4(I) indicates the digit 9 four pulses above 5).

Receipt of B digit Let it be assumed that the next digit is greater than or above 5, such as the digit 8. The counting tubes will progress as above described for the first five pulses such that at the end of the fifth pulse the following conditions appear:

(1) Relay L( I) has reoperated at the end of the fifth pulse;

(2) Tube P5( I) is conducting and all other tubes are extinguished; and

(3) Relay P2( I) is operated and locked.

Upon conduction through tube P5(I) the oathode of tube P5(I) rises to substantially 100 volts positive potential with respect to negative battery, thereby conditioning varistor I46 such that the latter will represent a high impedance to the next pulse on conductor I22. The cathode of tube P5(I) also applies this high positive voltage to the right-hand or arrow side of rectifier I40 connected to rectifier MI in the starter electrode circuit of tube PI (I This positive voltage on the right-hand side of rectifier I40 effectively makes rectifier I40 a low impedance to positive pulses on conductor I22, thereby in effect making rectifier I4I a high impedance to such pulses. There- 'fore, upon the next pulse, that is, the sixth pulse on conductor I22, both tubes A5(I) and PI(I) will fire.

When relay L(I) releases during the sixth pulse, condenser H6 is discharged. When relay L(I) reoperates at the end of the sixth pulse. the pulsing conductor I22 will have applied thereto a high positive pulse from the pulse transformer I23. This positive pulse on conductor I22 will fire both tubes A5(I) and PI(I). Tube PI (I) upon conducting, extinguishes tube P5(I) since both of these tubes use the same common anode load resistance III and impedances [I2 and I I3, as has been explained previously. Tube A5( I) conducts in a circuit extending from negative battery, to cathode of tube A5(I), across the main anode conducting path tube A5( I through the winding of relay A5(I), to positive battery on the off-normal conductor I09, thereby operating relay A5( I Relay A5( I upon operating, releases relay BS(I) by opening the operating circuit for the latter relay at contact 2 of relay A5(I).

Tube A5(I) remains conducting and relay A5(I) remains operated for successive pulses of the same digit.

In response to the seventh positive pulse on the pulsing conductor I22, tube P2(I) fires, extinguishing tube PI (I). Furthermore, upon the eighth pulse on conductor I22, tube P3(I) con-' over ccntact 3 of -relay- RA(I) to the left-hand or arrow side of the pair of rectifiers I48 and I49. These rectifiers, under the action of the positive potential on their arrow sides, will act as low impedances, whereupon positive battery is extended through rectifier I40 directly to conductor I1I. Positive voltage is extended through rectifier I49 and over contact 1 of relay A5(I) to conductor I11. Positive battery on conductors HI and I11 is extended over respective contacts 4 and I of the B digit steering relay BS(2) to the left-hand sides of the windings of respective B digit register relays BI(2) and B1('2). The current flowing through the windings of relays BI (2) and B1(2) increases sufliciently to operate these two relays, thereby registering on a twoout-of-five code basis the B digit 0 by the operation of the B digit register relays BI(2) and B1(2).

Relay RA(I) upon operating extends ground over its contact 1, contact I of relay A5(I), to ground the main anode of tube A5(I), thereby extinguishing tube A50). Relay RA(I), upon operating, also extends positive battery over its contact 8, to resistance I81 to discharge condenser I01 and refire tube ST(I), thereby extinguishing tube P3(I) to revert the counting tube chain to its normal condition. Ground is extended from contact 6 of relay ON (I), over contact 5 of relay P2(I), over contacts 9 and I0 of relay RA(I), over conductors I00 and IN. Ground on conductor I00 extends over contact 9 of relay AS(2) and contact 9 of relay BS(2) to hold relay BS(2) operated when the locking circuit therefor is broken upon the operation of the next steering relay CS (not shown). Ground on conductor IOI is extended over contact II of relay AS(2), contact I0 of relay BS(2) over conductor 203, to negative battery through the winding of the next steering relay CS (not shown) which operates and locks to off-normal ground on conductor I02 under the control of the next or DS steering relay (not shown).

When relay RA(I) is released, during the first pulse of the next digit, the previously operated steering relay BS(2) releases leaving the subsequently operated steering relay CS (not shown) operated and locked under control of the fourth steering relay over ofi-normal ground on conductor I02 preparatory to operating on a twoout-of-five basis the 0 digit register relay (not shown) of Fig. 2.

Subsequent digits The receipt, detection, counting, steering and registering of subsequent digits are accomplished similarly to the above discussion and further detailed analysis of the circuit operation is considered unnecessary.

Checking circuit The checking tube CK(I), with associated circuits, is provided to indicate the failure of any tube STU) through A5(I) to ionize at a time when its respective ionization should occur.

It will be noted that the pulsing conductor I22 is connected to resistance I29 and through condenser I23 to ground at the starter electrode circuit of tube CK( I It will also be noted that at any time prior to the production by transformer I23 of a positive pulse on the pulsing conductor I22, condenser I28 acquires a negative charge in the circuit extending from ground, through condenser I28, through resistance I29,-'over contact I of relay SR'( I),'to negative battery .thro'ughthe windings I and I06 of the pulse transformer I23. At such time as the pulse transformer I23 produces a positive pulse, this positive pulse is applied to the starter electrode circuit of tube CK(I). will be held there due to the presence of condenser I28 for a length of time depending upon the time constant of the circuit involving resistance I29 and condenser I28. This means that the positive pulse on the pulsing conductor I22 will not be made effective to fire tube CK(I) until a measured interval of time after the application to that pulsing conductor I22 of the positive pulse generated by the pulse transformer I23. At such time as the voltage on condenser I28 shall have risen to a positive value sufficient to fire tube CK(I), ionization will occur across the starter electrode gap of that tube, which ionization will be manifested in a discharge across the main anode discharge gap of tube CK(I) provided there is suff cient main anode voltage at tube CK(I) to sustain the discharge. If there is sufficient voltage at the main anode of tube CK(I), this discharge will occur in a circuit extending from negative battery through the winding of relay CK( I cathode of tube CK( I) main anode of tube CK( I) through the anode load resistance III and impedances H2 and H3. to positive battery on conductor I09.

It will be recalled that each of the tubes ST( I) through P5(I) has its main anode connected to positive battery through the same common anode load resistance III and impedances H2 and H3. These load impedances and resistance are arranged such that if any of the tubes ST(I) through P5(I) fires and conducts a main discharge current, the voltage drop through these common anode impedances will be sufiicient to reduce the main anode voltage of tube CK(I) sufficiently such that the tube CK(I) cannot sustain a main gap discharge.

It will be recalled that at the same time that the starter electrode timing delay circuit of tube CK(I) was measuring an interval of time, the pulsing conductor I22 applied to the starter electrodes of all of the counting tubes the high positive pulse. If that positive pulse fails to fire one of the tubes ST(I) through P5 (I) by the time that the condenser I28 in the starter electrode circuit of tube CK(I) fires tube CK(I), then a I main discharge current will be sustained in tube CK(I), operating relay CK(I) to indicate a signal of improper operation of the pulse counting circuit. On the other hand, if one of the tubes S.T( I )I through P5( I) does fire in response to the positive impulse on the pulsing conductor I22, then the main anode Voltage of tube CK(I) will have. been reduced sufficiently such that tube CK(I) cannot fire when the starter electrode thereof ionizes the starter electrode-cathode gap of tube CK(I).

It will be appreciated then that the tube CK(I), with its associated circuit elements, is a checking means for determining the failure or non-failure of one of the tubes of the counting chain to fire in response to an impulse on the pulsing conductor I22.

setting an idle marker When the originating register has registered, in its relays of Fig. 2, sufficient digits to Warrant seizure of an idle marker circuit for completion of the call, such a marker may be seized under the control, as disclosed by Busch and Dehn above, of the steering relays of Fig. 2. For in- The negative charge on condenser I28- stance, relay HS(2) will operate after the seventh or G digit (exclusive of an 11' prefix) has been registered. Relay HS(2) may be arranged to complete the marker start circuit after receipt and registration of seven digits, which maycomprise a complete calling number of three ofllce code digits and four numerical.

If an initial 11 prefix is detected and registered by the operation of relay IIX(I), relay BS(2) may complete the marker start circuit for seizing an idle marker after the X digit of the 11X code is registered in the A register of Fig. 2. In this case the operated relay IIX(I) may be arranged to transmit a special signal to the seize marker.

Completion of connection When an idle marker is seized, the information registered in the digit registers of Fig. 2, along with other information, is transferred to the marker on a two-out-of-five basis by ground on two out of five conductors from the contacts of I each group of register relays.

The marker releases the originating register, thereby returning all apparatus of Figs. 1 and 2 to normal, completes the indicatedconnection, and releases leaving the connection under the supervision of a trunk, for instance.

It is to be understood that the above described arrangements are illustrative of the application of the principles of the invention. vNumerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. In a signaling system, means for generatin at least one impulse, a gas-filled detecting tube for detecting said impulse, a gas-filled check tube, means for applying said impulse tosaid detecting tube to operate said detecting tube, delay means, means for applying said impulse simultaneously to said check tube through the agency of said delay means, signal means controlled by said, check tube, said check tube operable by said impulse to actuate said signal means only if said detecting tube fails to operate during the delay period determined by said delay means;

and means controlled by the operation of said detecting tube duringsaid delay period to prevent the operation of said check tube at the en of said delay period.

2. In a signaling system, means for generating at least one impulse, a gas-filled detecting tube for detecting said impulse, a gas-filled check tube, means for applying said impulse to said detecting tube to operate said detecting tube, a delay network, means for applying said impulse simultaneously to said check tube through said delay network, signal means controlled by said check tube, said check tube operable by said impulse to actuate said signal means only if said detecting tube fails to operate during the delay period determined by said delay network, and means interconnecting said tubes and controlled by the operation of said detecting tube during said delay period to prevent the operation of said check tube at the end of said delay period.

3. In a signaling system, means for generating at least one impulse, a gas-filled detecting tube for detecting said impulse, a gas-filled check tube, each of said. tubes comprising a cathode and a main anode and a starter electrode, means for applying said impulse to the starter electrode circuit of said detecting tube to cause conduction therein, a delay network in the starter electrode circuit of said check tube, means for applying said::impulse simultaneously. to.;the starter .elecrstrode circuit of .said' check'tube through said 'dela-y network, signal means controlled by said check tube, said impulse causing conduction in said check tube to operate said signal means only if said detecting tube fails to conduct during the delay period determinedby said delay network,

" load-common to both tubes, and means including said common load controlled by conduction in'said detecting tube during said delay period I to prevent conduction in said check tube at the end of said delay period.

- 4. In a signaling system, means for generating at least one impulse, a gas-filled detecting tube for detecting said impulse, a gas-filled check tube, each of said tubes comprising a cathode and a main anode and a starter electrode, means for applying said impulse to the starter electrode circuitof said detecting tube to cause conduction therein, a delay network in the starter electrode circuit of said check tube, means for applying "said impulse simultaneously to the starterelectrode circuit of said check tube through said delay network, signal means controlled by said check tube, said impulse causing conduction in said check tube to operate said signal means only if said detecting tube fails .to conduct during the delay period determined by said delay network, a main anode load common to both tubes, and means including said common main anode lead controlled by conduction in said detecting tube during said delay period to prevent conduction in said check tube at the end of said delay period. 5. In a signaling system, means for generating impulses, a plurality of gas-filled tubes for counting said impulses, a gas-filled check tube, means for applying said impulses simultaneously to all of saidcounting tubes, means for permitting only one counting tube to operate responsive to the first impulse, gating means interposed between said tubes for enabling operation of successive counting tubes in response to successive impulses, delay means, means for applying said impulses to said check tube through the agency of said delay means, signal means controlled by said check tube, said check tube operable by said imwpulses to actuate said signal means only if a counting tube Iailstobperate during the delay period determined by said delay means, and means controlled'by theopera'tion of any one of said counting tubes during said delay period to prevent operation of said check tube at the end of said delay period.

6. In a signaling system, means for generating impulses, a plurality of gas-filled tubes for counting'said impulses, a gas-filled check tube, means for applying said impulses simultaneously to all of said counting tubes, means for permitting only "one counting tube to operate responsive to the first impulse, gating means interposed between "said tubes for enabling operation of successive counting tubes in response to successive impulses, adelay network, means for applying said impulses to said check tube through said delay network, signal means controlled by said check tube,

said check tube operable by said impulses to actuate said signal means only if a counting tube cfails to operate during the delay period. determined by said .dela-y network; andmeansinterconnecting .said check tubejwith' each of'said counting tubes controlled by the operation of any one of said counting tubes during said delay period to prevent operationfof said check tube at the end of said delay period.

7. In a signaling system, means for generating impulses, a plurality of gas-filled tubes for counting said impulses, a gas-filled check tube, each of said tubes comprising a cathode and a main anode and a starter electrode, means for applyingsaid impulses simultaneously to the starter electrode circuits of all of said counting tubes, means for permitting only one counting tube to conduct responsive to. the first impulse, gating means interposed between said tubes for enabling conduction in successive counting tubes in response to successive impulses, a delaynetwork in the starter electrode circuit of said check tube, means for applying said impulses to the starter electrode circuit of said check tube through said delay network, signal means controlled by said check tube, said impulses causing conduction in said check tube to operate said signal means only if a counting tube fails to operate during the delay period determined by said delay network, a load common to said check and counting tubes, and means including said common load controlled by the operation of any one of said counting tubes during said delay period to prevent conduction in said check tube at the end of said delay period.

8. In a signaling system, means for generating impulses, a plurality of gas-filled tubes for counting said impulses, a gas-filled check tube, each of said tubes comprising a cathode and a main anode and a starter electrode, means for applying said impulses simultaneously to the starter electrode circuits of all of said counting tubes, means for permitting only one counting tube to conduct responsive to the first impulse, gating means interposed between said tubes for enabling conduction in successive counting tubes in response to successive impulses; a delay network in the starter electrodecircuit of said check tube, means for applying s pulse's.;to the starter electrode circuit of sae'cktube' through said delay network, signal I ns controlled by said check tubef'said impulses sing conduction in said check tube'to operate "said signal means only if'a counting tube fails to Ioperate during the 'delayperiod determined by said delay network,

a main anode lead common to said check and counting tubes, and means including said com- 7 mon load controlled by the operation of any one of said counting tubes duringsaid delay period to prevent conduction in said check tube at the end of said delay period.

ALBERT-E. BACHELET.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,801,657 Buyko Apr. 21, *1931 2,389,204 Ludl et a1 'Nov; 20, 1945 2,530,093 Speed Nov. '14, 1950 

